I don't see what college grades have to do with anything.
I graduated high school, washed dishes for two years and then got a well paid but awful job, saved money for flying lessons and worked my way up through towing gliders, flight instruction, air taxis, bush flying, corporate and finally airline flying, and after twenty seven years in the business am a reasonably competent captain of a 70 tonne airliner.
Despite never going to college I passed all the written examinations for my FAA ATP certificate and my UK ATPL first time, and have never failed a proficiency check at any level from private upwards. In order to operate an airliner you need to know the three and five times tables, be able to add a column of figures and carry one over when you get to sixty, and operate a simple calculator. And you need to know how to fly. But you don't need a college degree.